1. Field of the Invention
The present invention relates to a lock-up device for a fluid torque transmission apparatus, and more particularly relates to a lock-up device to transmit torque from an input rotary member and to absorb and to damp torsional vibration.
2. Background Information
A fluid torque transmission apparatus transmits the torque of an input member to an output member, and an example of such an apparatus is a torque converter.
A torque converter is an apparatus that has three kinds of bladed wheels (an impeller, a turbine, and a stator) in its interior, and transmits torque via a hydraulic fluid on the inside. The impeller is fixed to a front cover serving as an input-side rotary body. The turbine is disposed opposite the impeller in a fluid chamber. When the impeller turns, the hydraulic fluid flows from the impeller to the turbine, rotates the turbine, and outputs torque.
This type of torque converter often includes a lock-up device that transmits torque from the input rotary member to the output rotary member and absorbs and damps torsional vibration that is transmitted from the input rotary member to the output rotary member.
This lock-up device is disposed in a space between the turbine and the front cover, and directly transmits torque from the front cover to the turbine by mechanically linking the front cover and the turbine.
This torque converter usually has a disk-shaped piston, a retaining plate, an elastic member, and a driven plate. The disk-shaped piston is configured to be pressed against the front cover. The retaining plate is fixed to the outer peripheral part of the piston. The elastic member is supported elastically deformably by the retaining plate. The driven plate supports the ends of the elastic member in the rotational direction. The driven plate is fixed to the turbine shell, for example.
When the lock-up device is in a linked state, the torque is transmitted from the front cover to the piston, and is further transmitted through the elastic member to the turbine. Also, with the elastic linking mechanism of the lock-up device, the elastic member is compressed in the rotational direction between the retaining plate and the driven plate, and absorbs and damps torsional vibration.
This lock-up device is sometimes provided with a support member that supports the outer peripheral part of the elastic member in the radial direction as shown in Japanese Laid-Open Patent Application 2002-48217.
With the lock-up device described in JP2002-48217, movement of the support member in the axial direction and the radial direction is restricted by the retaining plate. More specifically, part of the retaining plate extends to the transmission side of the support member in the axial direction, and when the support member moves in the axial direction to the transmission side, the retaining plate restricts the axial direction movement of the support member by coming into contact with the support member. Therefore, the retaining plate may end up having a complex shape, which drives up its manufacturing costs.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved lock-up device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.